It has long been known to provide lighting to stages, theaters and other environments with the use of individual light sources hung from trusses or fixed structural members mounted adjacent to the area to be lit. Some light sources are used as wash or general stage illumination, while others of the light sources are used as spots for highlighting specific positions on stage, portions of an actor's body or the like. Other similar light sources are used in such environments as homes or offices.
Previous light sources have utilized colored celluloid gels which may be interposed in the light beam to change the lighting color. In addition, prior systems have used various techniques to vary the beam divergence and the intensity of the light beams.
Systems have also been heretofore developed for automatically varying the position, color, intensity and beam divergence of lighting sources used for the stage or theater. For example, U.S. Pat. No. 4,392,187, issued July 5, 1983 and entitled "Computer Controlled Lighting System Having Automatically Variable Position, Color, Intensity and Beam Divergence," by the present applicant, discloses a computerized lighting system where a plurality of light parameters may be automatically controlled. In U.S. Pat. No. 4,392,187, dichroic filters are movable within a light beam to vary the transmitted color from the light source. In this patent, one technique for utilizing dichroic filters causes aligned filters to be pivoted within the light beam to vary the angle of incidence of the light upon the filter. Integration lenses are required to mix white light with the colored light. Another technique disclosed in the patent utilizes rotatable disks having a plurality of dichroic filters which maya be variably indexed with one another in order to change the color of the light source.
While the system disclosed and claimed in U.S. Pat. No. 4,392,187 has been found to work well in actual practice, a need has arisen for a technique for using dichroic filters to vary the hue and saturation of a light beam which provides improved control, improved mechanical operation and reliability, and the capability of being very compactly packaged with a minimum of expensive components such as integration lenses and the like.